As the bandgap of nitride-based material covers entire visible light range, optoelectronic devices such as light-emitting diodes (LEDs) fabricated by nitride-based materials are widely applied in fields like solid display, lighting and signal lights. The non-toxic nitride material has such advantages as high luminance, low work voltage and easy for miniaturization. Therefore, it is an irreversible trend to replace conventional light source with GaN-based light emitting diode. However, one of the keys to obtain nitride light emitting device of higher light-emitting efficiency lies in the improvement of photoelectric conversion efficiency and light extraction efficiency.